1. Field of the Invention
This invention relates generally to perpendicular magnetic recording systems, and more particularly to perpendicular magnetic recording write heads for use in magnetic recording disk drives.
2. Description of the Related Art
In a perpendicular magnetic recording system like a magnetic recording hard disk drive, the recorded bits are stored in a perpendicular or out-of-plane orientation in the recording layer. The recording or write head in perpendicular magnetic recording disk drives includes a write pole comprising a shaped pole and a main pole for writing to the recording layer, and one or more return poles for return of magnetic flux from the recording layer.
The main pole is typically formed by electroplating a high moment magnetic material, the most common example being cobalt-iron (CoFe) alloys. To form the main pole, in one technique referred to as the Damascene process, a generally trapezoidal shaped trench with sloped sidewalls is formed in a substrate. A metallic material like Ru is deposited in the trench to serve as a side gap layer for the main pole. The main pole may be electroplated onto a pole seed layer, such as a NiCr/CoFe bilayer, which is known to produce the soft magnetic property (low coercivity) desirable for the subsequently electroplated CoFe main pole. The NiCr/CoFe pole seed layer may be grown on top of an amorphous underlayer to break the effect of the crystalline orientation of the underlying Ru side gap layer on the CoFe main pole. In the prior art, a metal oxide material like alumina (Al2O3) is typically used as the amorphous underlayer prior to deposition of the NiCr/CoFe pole seed layer. Because the metallic side gap layer, for example Ru, is formed first before the NiCr/CoFe pole seed layer and electroplated CoFe main pole, it also serves as an electroplating seed for conduction of the electroplating current. However, while a metal oxide underlayer like alumina provides excellent growth for the NiCr/CoFe pole seed layer, it insulates the electroplating structure from the underlying Ru side gap layer. As a result, the current-carrying capacity originates solely from the NiCr/CoFe pole seed layer and is drastically reduced due to alumina insulation of the Ru side gap layer.
What is needed is a perpendicular magnetic recording write head with a main pole formed on an amorphous underlayer that produces low coercivity in the main pole and does not insulate the electroplating structure.